Cytosolic PSD-95 interactor alters functional organization of neural circuits and AMPA receptor signaling independent of PSD-95 binding

• Published in: Network neuroscience (Cambridge, Mass.) Vol. 5; no. 1; pp. 166 - 197
• Main Authors: Rodriguez, Ana R., Anderson, Erin D., O’Neill, Kate M., McEwan, Przemyslaw P., Vigilante, Nicholas F., Kwon, Munjin, Akum, Barbara F., Stawicki, Tamara M., Meaney, David F., Firestein, Bonnie L.
• Format: Journal Article
• Language: English
• Published: One Rogers Street, Cambridge, MA 02142-1209, USA MIT Press 01.02.2021; MIT Press Journals, The; The MIT Press
• Subjects: AMPA receptors; Binding; Circuits; Clustering; Computational neuroscience; Cypin; Density; Electrophysiology; Firing rate; Functional morphology; Glutamic acid receptors; Glutamic acid receptors (ionotropic); Hippocampal neurons; Localization; Microelectrode array; Microelectrodes; Mutants; N-Methyl-D-aspartic acid receptors; Networks; Neural circuits; Neural networks; Postsynaptic density; Postsynaptic density proteins; Proteins; Receptor density; Receptors; Synapses; Synaptic density; Synaptosomes; Toxicity; Waveforms; α-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid; α-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors; Electrophysiology; Hippocampal neurons; Microelectrode array; AMPA receptors; Neural circuits; Cypin
• ISSN: 2472-1751; 2472-1751
• DOI: 10.1162/netn_a_00173

Cytosolic PSD-95 interactor (cypin) regulates many aspects of neuronal development and function, ranging from dendritogenesis to synaptic protein localization. While it is known that removal of postsynaptic density protein-95 (PSD-95) from the postsynaptic density decreases synaptic N-methyl-D-aspartate (NMDA) receptors and that cypin overexpression protects neurons from NMDA-induced toxicity, little is known about cypin’s role in AMPA receptor clustering and function. Experimental work shows that cypin overexpression decreases PSD-95 levels in synaptosomes and the PSD, decreases PSD-95 clusters/μm , and increases mEPSC frequency. Analysis of microelectrode array (MEA) data demonstrates that cypin or cypinΔPDZ overexpression increases sensitivity to CNQX (cyanquixaline) and AMPA receptor-mediated decreases in spike waveform properties. Network-level analysis of MEA data reveals that cypinΔPDZ overexpression causes networks to be resilient to CNQX-induced changes in local efficiency. Incorporating these findings into a computational model of a neural circuit demonstrates a role for AMPA receptors in cypin-promoted changes to networks and shows that cypin increases firing rate while changing network functional organization, suggesting cypin overexpression facilitates information relay but modifies how information is encoded among brain regions. Our data show that cypin promotes changes to AMPA receptor signaling independent of PSD-95 binding, shaping neural circuits and output to regions beyond the hippocampus. We used lentivirus to overexpress cytosolic PSD-95 interactor (cypin) and a cypin mutant that cannot bind PSD-95 (cypinΔPDZ) to understand how cypin regulates synaptic signaling. Using biochemical and electrophysiological approaches, we show that cypin, but not the cypin mutant, regulates synaptic PSD-95 content. Surprisingly, cypin overexpression increases AMPA receptor function independent of its role in PSD-95 localization, while cypinΔPDZ overexpression causes networks to be resistant to CNQX-mediated changes to local efficiency. We then developed a computational model to account for the effects of cypin overexpression, finding that our simulated model also demonstrates a role for AMPA receptors in cypin-promoted changes to neural circuits. These results support a role for cypin in controlling synaptic function at synapses that is distinct from regulation of PSD-95 function.